Carrier billing lets you buy apps, music, or subscriptions and have the cost...

https://www.nav-bookmarks.win/carrier-billing-lets-you-buy-apps-games-or-digital-content-and-have-the-cost

Carrier billing lets you buy apps, music, or subscriptions and have the cost added directly to your phone bill. If you use a pay-as-you-go plan, the purchase amount is taken from your available credit instead